This invention relates to electrophotographic process cartridges having toner and is directed to sensing the exhaustion of toner so that such information can be signaled to the imaging machine operator or otherwise acted upon.
A number of alternatives are known for sensing the amount of toner is an imaging process cartridge. In cartridges in which a toner paddle stirs the toner during operation, the paddle has been driven through a torque sensitive drive train and the torque sensed has been used to determine the amount of toner remaining. The toner-low sensing of this invention is believed to be more accurate and more cost-effective than such systems in practices.
Similarly, the amount of toner has been determined by weighing the cartridge, with the reduction in weight defining the use of toner. This requires accurate knowledge of the empty weight of the cartridge and accurate weighting mechanism in the printer in varying environment and over the life of the printer. The toner low sensing of this invention also is believed to be more accurate and more cost-effective than such systems.
A number of optical systems are known, using transparent windows in the toner cartridge and optical paths through the toner. In some of these systems a relative small well is formed in the cartridge for toner to occupy, and an optical source is positioned on one side of the well and an optical receiver is positioned to receive light which passes through the well. If no or very low level of light reaches the sensor, this is interpreted as toner still being in the cartridge at the level of the well. It is known to have the well at or near the bottom of the cartridge so as to sense toner exhaustion or near exhaustion. Some of such optical paths might be somewhat complex or lengthy. The toner low sensing of this invention employs optical sensing, but in a short path and without a well.
In accordance with this invention, the cartridge may have a single window wide enough to permit light to enter the cartridge from a source in the imaging device, be reflected, and then return through the window to a sensor in the imaging device. The window is positioned near the bottom of the toner chamber. The cartridge has a long dimension and has an internal stirring paddle mounted along the long dimension. The cartridge has at least on side generally perpendicular to the long dimension of the cartridge in which the window (or windows) is located. A reflector is mounted in the toner chamber, also near the bottom of the toner chamber, parallel to the window, and not more than 40 millimeters from the window. The paddle carries a compliant blade across the window and the reflector to clean them for sensing.
A high level of light from the source reaching the sensor senses toner low. Because of the positioning near the bottom of the toner container, the most critical information indicative of toner exhaustion is obtained in an accurate and cost-effective system.